Process of refining mineral oils



Feb. 24, 1942. A. LYMAN 2,274,373

PROCESS OF REFINING MINERAL OILS Filed Dec. 11, 1959 2 Sheets-Sheet '1DIST! LLATE PH ENOL WATER wg RAF-MATE- DISTILLATE PHENOL WATER a La- Q125" as 27 2 29 FIRSTEXTRACT sgco 2 INVENTOR ARTHUR L. LY MAN ATTOBNEYFeb. 24, 1942. A. L. LYMAN PROCESS OF REFINING MINERAL OIIJS Filed Dec.11, 1939 2 Sheets-Sheet 2 INVENTOR ARTHUR L. LYMAN- Patented F eh. 24,1942 UNITED STATE s PATENT OFFICE. r

PROCESS OF REFINING MINERAL OILS Arthur L. Lyman, Berkeley, Calif.,assignor to Standard Oil Company of California, San Francisco, Calif., acorporation of Delaware Application December 11, 1939,-Serial No.308,714

10 Claims. (01.196-13) This invention relates to improved processes forrefining mineral hydrocarbon oils, and has particular reference tomethods of separating crude petroleum oils or their distillates intofractions or components of different chemical com- 'pos'itions,wherebyoils of high and of low viscosity index may separately be obtained fromcrude oils ortheir distillates normally characterized by an inferiorviscosity temperature relationship or a low viscosity index.

As is well known, lubricating oils from Pennsylvania crude petroleumshave higher viscosity indexes (as the term viscosity index is defined byDean & Davis in Chemical and Metallurgical Engineering, 1929, volume 36,pages 6184519) than those oils obtained from Mid-Continent, Gulf, Mexicoor California crudes. It is a purpose of my invention to provide methodsof extracting from such low viscosity index oils, by

means of selective solvent refining agents, those hydrocarbonsresponsible for this inferiority (generally understood to be ofunsaturated, aromatic and/or naphthenic molecular structure), thusproviding oils consisting wholly or largely of those hydrocarbonscharacterized by high viscosity indexes (generally understood to be ofparafilnic molecular structure);

One of the chief sources of concern to the oil refiner is to prepareoils having a high viscosity index and at the same time obtainsatisfactory yields of such highly refined rafiinates. These twoobjectives have heretofore appeared to be in an oil of inferior index,only those hydrocarbons highly unsaturated, aromatic and/or naphthenicin character, and has nomaterial effect in removing from the oil thosehydrocarbons intermediate between the highly aromatic and/or naphthenic,on the one hand, and the highly parafiinic, on the other hand. In theuseof such a highly selective solvent the refiner obtains an extract smallin volume and highly unsaturated or aromatic in composition, and araflinate large in volume, but of only moderate increase in viscosityindex and degree of refinement. If he attempts to prepare an oil ofhigher viscosity index" and higher degreeof refinement from a lowviscosity index crude or distillate, 'the refiner is other substanceswhich were added to obtain desired characteristics. 7

solvents.

solvent power than those which are designated herein as highlyselective. Such a solvent is relatively less selective and-removes insolution both highly aromatic hydrocarbons and large amounts of thosehydrocarbons occupying a position intermediate between the highlyaromatic and/or naphthenic, on the one hand, and .highly'paraifinic, onthe other hand, and is therefore relatively non-selective'when appliedto oils of initially low viscosity index. In the use of such relativelynon-selective solvents, the objective of .a highly refined rafiinateisobtained, but only at .a substantial sacrifice in yield. The rafiinateis very small in volume and the major proportion of the oil is removedas the extract, whichhas little utility except as fuel for, as in thecase of small volumes of extracts obtained in the use of highlyselective solvents, for such purposes as take advantage of the aromatic,unsaturated and/or naphthenic compounds present.

In attempting to overcome these. difiiculties and to increase theyieldof high viscosity index rafiinates, various systems have been suggestedfor more efficiently treating oils withselective In the conventionalmethods of solvent extraction used industrially, the solvent chosen hasbeen applied to the oil (whether by single batch, multiple batch, stage'counterfiow, or

countercurrent systems), as a single pure substance or as a constant anduniform mixture with Fractional precipitation has also been ,proposed invarious patents as a method of refining mineral oils. In this type ofprocess the entire mineral oil fraction is dissolved in a solvent whichinitially has no selectivity by reason of the fact' that it dissolvesthe entire oil fraction. [Thesolvent capacity of this solvent has beendecr eased in various ways to free portions of thedissolved oil. Onesuch way has been by dilution. So far as known to me, such methods ofrefining oils do not give yields of, high viscosity index raffinatescomparable to those obtained by the present invention. c

It is therefore an object of this invention to 'provide a process ofrefining oils which efiects an increased yieldof a given high, viscosityindex raffinate, as compared with prior processes of extraction. i

Another object is to provide a process of refining, mineral oils whichutilizes a novel method and order of steps of combining phenol and aforced to use a solvent agent with much higher 55 diluent oranti-solvent, suchas water, during a selective solvent extractionprocess.

An additional object of the invention is to provide a process whichenables accurate control of the quantity of diluent or anti-solventadded to a selective solvent, and which simultaneously decreases thecost of reclaiming the solvent.

A still further object of the invention is to provide a process ofefiiciently extracting mineral oils with selective solvents, in which anoil to be extracted, a selective solvent substantially saturated withhydrocarbons dissolved from an oil, and a diluent or anti-solvent aresimultaneously mixed, in order to displace the more parafiinichydrocarbons dissolved in the solvent by the more aromatic, unsaturated,and/or naphthenic hydrocarbons contained in the oil to be extracted.

A still further object of the invention is to provide a closed cyclicsystem of selective solvent extraction and of solvent recovery whichutilizes residual heat from the distillation process in the extractionsystem.

Another object is to provide a recovery system for a selective solventcontaining a diluent which facilitates control of dilution steps in theselective solvent extraction system.

To carry out the process of this invention, I select a solvent refiningagent which in its undiluted state .is relatively non-selective asmeasured by its ability to separate aromatic, un saturated, and/ornaphthenic from paraifinic hydrocarbons. My preferred solvent is phenol,although the principle of my invention is not confined to treatment withphenol. It will apply to treatment with aniline, furfural, cresol, orany selective solvent which does not chemically react with the diluentor anti-solvent utilized, but is capable of dilution therewith toproduce a solvent having greater selectivity. The use of the generalclass of known selective solvents in the combination of steps andsequence of operations herein disclosed is contemplated as fallingwithin the broader aspects of the invention. Thus nitrobenzene, cresylicacid and chlorinated ethers, such as BB dichlorethyl ether, compriseexamples of known selective solvents and are operative in my process.Selective solvents in which water is miscible are preferred since wateris one of the most efi'icient diluents or anti-solvents which I havediscovered.

It should also be understood that diluents other than water are embracedwithin the generic scope of this invention. Diluents or anti-solventswhich are miscible with the solvent to be used, immiscible with the oilat extraction temperatures and which increase the selectivity of thesolvent upon addition in small amounts are perative for my purposes.Phenol and water comprise a preferred combination of solvent andanti-solvent for use in this invention.

Although selection of a proper solvent and a proper diluent is essentialto the success of my process, I do not claim as my invention theselective solvents and diluents alone, but rather the particular manneror order in which they are combined during the extraction process.

In practicing this invention it is preferred that the oil be extractedfirst with a selective solvent in its most dilute and most highlyselective state and then with a solvent in a less dilute and a lessselective state. By utilizing this particular order of steps, I havefound that an'increased yield of raftinates is obtained.

In the accompanying drawings, flow diagrams illustrate various processesutilizing the principles of my invention.

Figure 1 illustrates a seven-stage counterflow extraction process inwhich water is added as a diluent or anti-solvent at the fourth stage.

Figure 2 shows a combination of two extraction processes, the firstbeing a three-stage counterflow process in which water is added to thesolvent in the first two stages, and the second being a four-stageanhydrous phenol extraction treatment.

Figure 3 illustrates a seven-stage counterflow phenol extraction processcombined with a phenol recovery plant which produces substantiallyanhydrous phenol to be returned to the extracting system, and watercontaining phenol to be used as adiluent.

These three specific examples of processes utilizing my invention willnow be described in detail.

Figure 1 shows a seven-stage counterflow extraction system in which thedistillate flows from left to right through mixer l8, separator l8,mixer I9, separator l9, etc. to mixer 24f and separator 24. Theundissolved, refined distillate is removed from the top of separator 24to storage. The selective solvent, phenol being typical of the typepreferred, flows from right to left through mixer 2 5' to separator 24,then to mixer 23' and separator 23, etc., back to mixer 18 and separatorl8. The extract removed from separator 22, which comprises solvent andits dissolved hydrocarbons, is simultaneously diluted with water andmixed with the raffinate from separator 20, in mixer 2|. It has beenfound that during this step the more parafiinic hydrocarbons dissolvedin the extract are freed from solution and replaced by the moreunsaturated, aromatic and/or naphthenic hydrocarbons present in theraffinate from prior extraction stages l8, l9 and 20. Some of the freedparafiinic hydrocarbons pass on through the following successiveextraction stages to give an ultimate increased yield inraffinate. Inthe systems herein described, the freed hydrocarbons are not actuallyseparated and separately identified. It is obvious, however, that wherea 10% increase in quantity of rafiinate is obtained this increase cancome only as a result of the hydrocarbons freed by dilution passing onthrough the extraction system with the raflinate. This result isentirely unexpected and unpredictable since it would seem thathydrocarbons once extracted by the selective solvent would again bedissolved with equal facility. Even more surprising is the fact thatsuch increases in yield of raffinate can be obtained without sacrificein the viscosity index of the refined oil.

Although I have not found it necessary to separate the hydrocarbonsfreed from the extract by dilution, such a separation is regarded aswithin the broader scope of the invention so long as the hydrocarbonsfreed by dilution are retained in the extraction system for furthertreatment.

Also, it is to be understood that the extract, rafiinate from stage 20and water need not be simultaneously mixed as shown in Figure 1,although this procedure constitutes an efficient and advantageous modeof operation. The water may be introduced into the extract either beforeor after it is moved with the railinate being treated.

A dewaxed distillate from Kettleman Hills, California crude oil wastreated by the method of Figure 1. The conditions of treatment and theresults obtained as compared with a similar tainable by my process.

conventional seven-stage counter-current process are given in thefollowing data:

1 pIs'rrLLA'rE TREATED Treat- Treat- Tre'at- Treatment ment ment mentNo.1 No.2 No.3 No.4

Gravity, A. P. I .4. 18.4 18.0 19. 7 1.9.9 Flash, F 460 455 465 445Viscosity at 210 F 89 93 81 81 TREATMENT Phenol selective solvent(volume percent) 215 280 211 312 Water added (percent by wt.

based on phenol) None 2. None 4. 4 Temp. of extraction, F 120 130 120130 RAFFINATE (UNDISSOLVED OIL) Yield (percent of original distill e) 3134 43 47 Gravity, A P I 28.6 29.0 *28.0 *27.6 Flas "F 445 450 465 450Viscosity at 100 F 520 530 534 613 Viscosity at 210 F 63 64 64 68Viscosityindex 90 93 91 90 EXTRACT (OIL REMOVED BY SOLVENT) Gravity, A.P. I 13. 2 12. 3 12.1 11. l Viscosity at 210 F-. 150 151 150 170*Inspections refer to dewaxed raiiinates, yields to waxy railinates.

Attention is directed to the fact that the above data show that adistinct increase in yield of rafiinate for the same degree ofrefinement is ob-- Comparing treatments yields substantially anhydrousphenol and also a water traction which contains phenol and which issuitable 'for use as a diluent.

In Figure 3 mineral oil distillate to be extracted fiows from left toright through mixer 40, separator 40, mixed II, separator II, to mixer46' and separator 46. The raflinate as extracted is removed from the topof separator 46 to storage tank'33 and retained for phenol recoverytreatment. The extracting solvent flows from right to left enteringthesystem at mixer 46' andleaving at separator 40 through pipe line IIto storage tank I02.

A diluent comprising water which may also contain some phenol, isadmitted in desired quantities to the system. Valves 61 to 16 inclusivepermit flexibility in the addition of this diluent. The system permitsaddition of water or other diluent at any single mixer or to -'anycombination of mixers desired. For example, with valve 6| open so thatwater flows to the systemthrough pipe I49, water may be admitted tomixers 40' l and 3 with'2 and 4 respectively, an increase'ofapproximately 10% in the quantity of refined oil is obtained with nomaterial sacrifice in the degree of refinement. In treatment number 2,not only was a 10% more rafimate obtained than in the conventionalnumber ltreatment but also an actual increase in the'viscosity index ofthe refined oil resulted. The increase in yield of refined oil is ofgreat importance and tremendous advantage in commercial operations.

Figure 2 discloses a combination process utilizing successive dilutionsteps in the first two stages of extraction. The distillate to betreated flows from left to right as in the previous figure and isremoved to storage from the last separator designated 3I in thedrawings. The hydrocarbons freed from the extract by th dilutions inmixers .and 26' are retained in the system in the I same manner as inFigure 1.

The last four stages of the process involve a "stage countercurrentextraction with a substantially less dilute and less selective solvent,preferably phenol. Ihis relatively less selective solvent is introducedin mixers 21' and 3| at the third and seventh stages and flows fromright to left.

v The extract from the first system (stages 25, 26 and 27) is removedfrom separator 25 and stored as a highly aromatic and/or unsaturatedfrac-' tion. At such time as is convenient the phenol and dissolvedhydrocarbons are separated and recovered therefrom. The extract from thesecond system (stages 28, 29, 30 and 31). is likewise removed fromseparator 28 and stored as an extract of a less aromatic and/orunsaturated character.

Figure 3 is an example of a system for extracting. a [distillate withphenol or alike equivalent solvent combined with a system of recoverywhich and 44 only, by opening valves 61, 60, 69, 10 and 15 and closingvalves 1I,12, 13, and 14. Likewise, water maybe added to all mixers 40to inclusive, and the quantity admitted to each mixer controlledindependently of others by adjusting metering valves 61, 12, 13, 14, '15and 16, corresponding to mixers'40', 4|, 42', 43', 44 and '45,respectively.v By utilizing metering valves of suitable well known typesat 61, 12, 13, 14, 15 and 16 accurate adjustment and control of thequantity of diluent may be obtained.

Valve connecting the phenol line I48 and the water line I49 enables aproper balance to be maintained between the water and the phenol. Forinstance, the percent error due to inevitable inaccuracies andvariations in the quantity of diluting fluid added, may be decreased byincorporation of phenol in the diluting water.

In the above connection it is pointed out that for any given error involume of diluent added, the error in the quantity of water incorporatedwill be reduced one-half if the diluent contains 50% phenol, toone-fourth if the diluent contains 75% phenol, etc. It is apparent thatsuch an expedient enables extremely accurate control of the quantity ofwater incorporated in the extracting system. Inasmuch as smallvariations in the amount of water effect profound changes in theselectivity of the extracting solvent, it is also apparent that accuratecontrol of the quantity of water is essential to satisfactory operationof my process. This desired accurate control can be obtained byutilizing as the diluent or anti-solvent, water containing phenol. It ispointed out that water containing up to 80% phenol acts as ananti-solvent and has no selective solvent action on mineral oil. Thewater used asa diluent should therefore contain no more than 80% phenol.

The system for recovering phenol from the extract and from the raffinatewill now be described. In Figure 3, I02 is the storage tank or surgedrum which receives the extract from the extracting system. From thestorage tank I02, the extract enters the recovery plant through pipe I03controlled by valve I04. Pipe I03 is connected to two heat exchangersI05 and I06 as shown, After passing the heat exchangers which maybeeither in series as shown or in parallel, the oil flows through anextension of pipe I03 to a control valve I42 and into flash chamber I01.The chamber I01 may be extended as shown to form a vertical column whichdenser IIO, thence to a receiver III. To the top of thereceiver IIIthere is, connected a gas line [12 leading; to apump;II3 whereby areduced pressure may be maintained on column I'I and on the materialflowingthrough line I03.;The condensate collectedin receiver I I I iswithdrawn through a branched pipe H4 equipped with control valves H5 andH6 whereby, when desired,

a portion of the condensate may be returned to the column I01 as areflux for the condensation of oil vapors, and to effect their return tothe lower section of the column. The remainder of the condensate fromreceiver III is run to a storage tank I I1.

From the bottom of column I01 a conduit II8 leads to a valve I20 andpump II9 which discharges through an extension of conduit II8 to theheater I22 and thence through coil I2I and pipe I23 to the side offractionating column I24, equipped with bubble cap plates I25 orequivalent construction as is Well known for such use.

The bottoms from column I24 flow through pipe I26 and valve I21 to theside of column I35 equipped with bubble plates and operated at apressure lower than in column I 24. The vapor line I44 from the top ofcolumn I35 may be connected to a condenser, but is preferably connectedas shown to the lower part of the column I01, thus resulting in a lowerpressure in the column I35. The lower part of column I35 is equippedwith heating means. Such a means is shown as a fixed external heater I43and a circulating line including pipe I40, pump I4I, heating coil I42and a return pipe therefrom to the fractionating column. Unvaporizedresidue from the bottom of the column I35 is drawn through line I31 bypump I38 and flows through the heat exchanger I06. From the exchangerI06 the cooled residue flows to the extracted oil storage tank I28.Provision is made for the introduction of a refluxing material into theupper portion of the tower I35 through line I45, controlled by valveI46.

Pipe line I26 described as connecting the bottom of column I24withcolumn I35, has a branch containing a valve which connects with lineII8 leading to heater I2I. By this means part of the bottoms from columnI24 may be recirculated through heater I2I to provide additional heatabsorbing medium.

The vapors from the top of column I24 flow to heat exchanger I05, thenceto receiver I30. The condensate fromreceiver I30 passes through branchline I3I equipped with valves I32 and I33 whereby a part of thecondensate may be returned to the column I24 to serve as a refluxmaterial, and the remainder may be passed to the phenol storage tankI34. This condensate constitutes substantially anhydrous phenol,

The raffinate from the solvent extracting system contains a small amountof phenol which is removed in a distillation column. This raifinatepasses from storage 33 through pipe I50 and control valve I64 to anappropriate distillation apparatus. The phenol vapors from thedistillation column pass to a condenser I54. The condensed phenol flowsthrough control valve I5'I and pipe I58 vto phenol storage tank I34. Aportion of the condensed phenol, as controlled by valve I56, may bereturned to the top of the distillation column as a refluxing material.

The rafiinate fiOWs to thebottom of the column as it is freed fromphenol. In order to supply heat for the distillation process, a portionof the still bottoms is continuously circulated through pipe I59, pumpI60, heating coil NH and heater I62, and then back through pipe I63 tothe column. The purified raffinite is removed to storage tank I65 as itaccumulates at the bottom of the still in excess of the amount necessaryfor circulation as a heating medium.

This recovery system combines with my extraction treatment to give aparticularly efficient and flexible process. By controlling pressure,temperature and amount of reflux in column IN the phenol content of thewater is determined. This in turn fixes the accuracy of control in theaddition of water to the selective solvent extraction system, aspreviously pointed out. Furthermore, by utilizing phenolic Water as adiluent or anti-solvent, a saving in distillation costs is efiected, inthat the necessity of completely separating the phenol and water iseliminated.

The entire method and apparatus disclosed in Figure 3 constitute aclosed system. After once charging reagents to the system it becomesunnecessary to add more water as diluent or more phenol as a selectivesolvent, except to replace losses from leakage or evaporation. Thesystem is self-contained and requires only adjustment of operatingconditions such as the rate of circulation of the diluent, and thetemperature of extraction to obtain the degree of refinement of themineral oil which may be desired. Also, by insulating storage tanks II?and I34 against heat losses and by adjusting temperatures of condensersI05 and H0, the temperature-of the extraction process can be controlledand residual heat of distillation simultaneously utilized in theextraction process.

From the above discussion it is apparent that the process of Figure 3 inparticular is not confined :to one which utilizes phenol as a solventand water as a diluent, but in its broadest aspects includes the use ofa selective solvent and a diluent or anti-solvent which renders theselective solvent more highly selective. Other examples of combinationsof solvents and diluents are cresylic acid with glycerol, phenol withethyl alcohol, phenol with ethylene glycol, phenol with BB dihydroxyethyl ether, and nitrobenzene with triacetin. The diluents oranti-solvents, glycerol, alcohol, ethylene glycol, BB dihydroxyethylether and triacetin, were practically completely immiscible withthe mineral oils treated and were miscible with the solvents in theamounts used. Each diluent was found to increase the selectivity of thesolvent and to be operative in the process of this invention.

The above diluents are representative of several types of organiccompounds as follows:

Ethyl alcohol is a low molecular weight aliphatic alcohol; methyl, ethyland normal propyl alcohol act as diluents or anti-solvents in thisprocess, but isopropyl alcohol and the higher alcohols are miscible withthe oil and are therefore undesirable.

Glycerol and ethylene glycol are polyhydroxy aliphatic alcohols. Othermembers of this class are trimethylene glycol, propylene glycol andpinacole (tetramethyl ethylene glycol).

Triacetin (glycerol triacetate) is an ester of a trihydroxy aliphaticalcohol and a low molecular weight aliphatic acid. Glycerol monoacetate,

glycerol diacetate, glycol diacetate and glycolldie formate are o herrepresentati'ves'of this class.

BB dihydroxy ethyl -ether is an aliphatic hydroxy ether in which twohydrogen atoms have,

traction.

In carrying out my processfthe quantityor" diluent desirable varies withthe type of mineral oil to be treated-and the degree of refinementdesired. With highlyaromatic oils, as much as water based on thequantity of'phenol has been used. Withmore parafiinic mineral oils,thequantity of diluent required is considerably less and depends, also,on'the ultimate degree of refinement to beefiected. As little as 2%water in phenol willlbe a sufficient-quantity of diluent for various ofthe more parafiinicoil's.

The selective solvent used in the final extraction stage need not beanhydrous; the essential features of this invention merely require thatthe solvent of the final stag should be no more selective than thesolvent in the first extraction stages. The amount of water or otherdiluent permissible in the solvent at the'finalstage varies with the oilstock being treated, with the refinement desired, and with the solventutilized;

, The temperature'of the xtraction process consitutes a variable whichpermits the degree of refinement to be altered at will. For any givensolvent, selectivity decreases with increasepf Obviously, temperaturevariations temperature.

representatives. of this may be correlatedwith the amount ct -dilutionof the solvent to obtain any. desired selectivity of solvent andrefinement of oil. i

It is, apparent that my process is not limited to use of apparatus ofthe type illustrated schematicallyin thedrawings. For instance, inFigmixers may be in the form of centrifugal pumps and the separators oieither the gravity or centriiugal type. It is not necessary that eachmixer and its corresponding separator should constitute separate unitsof apparatus since a single unit which accomplishes first the mixing andthen the separation would obviously be satisfactory.

The present application is a continuation-inpart of my copendingapplication Serial No.

' 87,874, filed June 29, 1936, which in turn may be regarded as in parta division of. mycopending application Serial No. 708,718, filed January29, 1934. The generic aspects of the invention involving first treatinga mineral oil distill-ate with a diluted highly selective solvent andthen treating the rafiinate from such an extraction with a substantiallyless selective solvent are claimed in m earlier application Serial No.798,718. The present case is directed to the species wherein the oilfreed from solution by dilution of an extract is retained in theextraction system.

I do not claim as my invention the distillation and 'recoverysystemofFlgure 3 alone, but claim only the particular combination with aselective solvent extraction treatment of the type herein disclosed.- 3Y Although certain specific amounts of solvent and otherspecificfeatures have been disclosed in my specification, it is'to be understoodthat all such changes and modifications as come within the scope of theappendedclaims are embraced within the spirit and teaching of myinvention.

I; claim: i i 1.;.-In a processof refining liquid mineralihydrocarbonswith a selective solvent refining agent which comprises extracting; thehydrocarbon, with. a selective solvent in a diluted and relativelyhighly selectivestate, separating the diluted solvent together with itsdissolved aromatic hydrocarbons from the remaining undissolved liquidhydrocarbons, extracting said undissolved frac-' tion with a selectivesolventin a substantially less dilute and relativelyless selectivestate, and separating the latter-solvent together with its dissolvedless highly aromatic hydrocarbons from the undissolved oil, the step ofdiluting at least one of said extracts with-an anti-solvent for the oilwhich is miscible with the selective solvent but ,immiscible with theoil torfree the more parafiinic hydrocarbons dissolved therein, andretaining the freed hydrocarbons in the extracting system.

2. In a process of refining liquid mineral hydrocarbons with a selectivesolvent refining agent which comprises extracting the hydrocarbon withphenol in a diluted and relatively highly selective state, separatingthe diluted phenol together with its dissolvedaromatic hydrocarbons fromthe remaining undissolved liquid hydrocarbons, extractingsaidundissolved' fraction" with phenol in a.

substantially less dilute and less selective state, and separating thelatter solvent together with its dissolved less highly aromatichydrocarbons from the dissolved oil, the stepof diluting saidlatter-extract with from 2 to 15% water to free the more parafilnichydrocarbons dissolved therein, and retaining the freed hydrocarbons inthe extracting system 3; In a process of refining liquid mineral oilswith a; selective solvent refining agent which comprises extractingv the"oil withphenol in a diluted and relatively highly selective state,separating the diluted solvent together with its dissolved aromatichydrocarbons from the remaining undissolved liquid hydrocarbons,extracting said undissolved fraction with phenol in a substantially lessdilute andrelatively less selective state, and separating the lattersolvent together with its dissolved less highly aromatic hydrocarbonsfrom the undissolved oil, the step of diluting at least one of saidextracts with phenolic water to free the more paraffinic hydrocarbonsdissolved therein, and retainingthe freed hydrocarbons in the extractingsystem. i

4. In a countercurrent process of extracting mineral oils with aselective solvent which comprises extracting the oil first with adiluted solvent in a highly selective state and then with a less dilutesolvent in a relatively less selective state, the step of diluting saidless selective solvent together with its dissolved hydrocarbons with ananti-solvent for the oil which is miscible with the selective solventbut immiscible with the oil while in intimate contact with anundissolved oil containing relatively nonparaflinic hydrocarbons,whereby the more parafilnic hydrocarbon constituents dissolved in thesolvent will be re- .stituentsin the undissolved oil.

5. A process of treating mineral oils which comprises treating the oilin countercurrent extraction with a selective solvent diluted withsuccessively decreasing proportions of water, the oil being treatedfirst with the most dilute and most highly selective solvent, wherebyfractions of decreasingly aromatic character are successively removedfrom the oil, distilling the water from said solvent and its dissolvedhydrocarbons, varying the proportion of solvent distilled over with saidwater inversely with the volume of diluent to be added in saidextraction process, separately distilling the remaining anhydroussolvent from the extracted oil, returning the solvent to the extractingsystem, and adding the aqueous distillate containing solvent as adiluent for increasing the selectivity of the solvent.

6. A process of refining liquid mineral hydro carbons with a selectivesolvent which comprises extracting the hydrocarbons with phenol in adiluted and relatively highly selective state, separating the dilutedsolvent together with its dlssolved aromatic hydrocarbons from theremaining undissolved liquid hydrocarbons, extracting said undissolvedfraction with phenol in a substantially less dilute and relatively lessselective state, separating the latter solvent together with itsdissolved less highly aromatic hydrocarbons from the undissolved oil,diluting at least one of saidextracts with water to free the moreparaffinic hydrocarbons dissolved therein and retaining the freedhydrocarbons in the extracting system.

7.A process of refining liquid mineral hydrocarbons with a selectivesolvent which comprises extracting the hydrocarbons with furfural in adiluted and relatively highly selective state, separating the dilutedsolvent together with its dissolved aromatic hydrocarbons from theremaining undissolved. liquid hydrocarbons, extracting saidundissolvedfraction with furfural in a substantially less dilute and relativelyless selective state, separating the latter solvent together with itsdissolved less highly aromatic hydrocarbons from the undissolved oil,diluting at least one of said extracts with water to free the moreparaffin'ic hydrocarbons dissolved therein and retaining thefreedhydrocarbons in the extracting system.

8I A process of refining liquid mineral hydro- Cir carbons with aselective solvent which comprises extracting the hydrocarbons with acresol in a. diluted and relatively highly selective state, separatingthe diluted solvent together with its dissolved aromatic hydrocarbonsfrom the remaining undissolved liquid hydrocarbons, extracting saidundissolved fraction with a cresol in a substantially less dilute andrelatively less selective state, separating the latter solvent togetherwith its dissolved less highly aromatic hydrocarbons from theundissolved oil, diluting at least one of said extracts with water tofree the more paraffinic hydrocarbons dissolved therein and retainingthe freed hydrocarbons in the extracting system.

9. A process for the separtion of mineral oil into fractions relativelymore paraifinic in character and relatively less paraflinic in characterthan the original oil, which comprises extracting said oil in aplurality of stages with a selective solvent for the non-parafiinicfractions of the oil and with an anti-solvent which is adapted to lowerthe solvent power of the selective solvent for the more parafiinic oilfractions and which is more soluble in the extract phase than in theraffinate phase, removing a rafiinate phase and an extract phase fromeach extraction stage, controlling the quantity of anti-solvent so thatthe proportion of anti-solvent is increased as the extraction proceedsfrom the stage at Which the final raflinate is withdrawn to the initialoil feed stage to free more parafifinic hydrocarbons dissolved in theselective solvent, and retaining the freed hydrocarbons in theextracting system.

10. A process for the separation of parafiinic and non-paraflinic oilfractions from a mineral oil containing the same which comprisescommingling said oil with a selective solvent for the non-paraifinicfractions and an anti-solvent adapted to lower the solubility of theparafiinic fractions in the selective solvent which is more soluble inthe extract phase than in the rafliniate phase, separating said phases,re-extracting the rafiinate with a selective solvent containing lessanti-solvent than in said first extraction and thereby forming a secondrafiinate phase and a second extract phase, precipitating parafi'inichydrocarbons dissolved in said second extract phase, and retaining saidprecipitated hydrocarbons in the system for additional extraction.

ARTHUR L. LYMAN.

